The present invention relates to an electromedical patient-monitoring system. More particularly, it relates to a system whereby body-condition-related information, provided by a body-contacting sensor, is amplified and processed for display or recording by an electrical monitor with minimum electrical hazard to a patient.
During recent years, the use of electromedical patient-monitoring systems has become widespread. A system such as may be used in an intensive care facility typically consists of several electrical sensors for providing information on heart rate, blood pressure, etc. The output from these sensors is amplified or otherwise processed, and transmitted to a monitoring device which may display or record the information, and may sound an alarm if a monitored signal is outside preset limits. Such monitoring devices, because of their power requirements, ordinarily are powered by 50 or 60 Hz AC line current. Intermediate amplifiers or signal processors may be either battery or line current operated. Since the sensors are normally in direct contact with a patient's body, it is obviously quite important to minimize the possibility of harm to the patient from electrical devices connected to the sensor.
Accordingly, it is a general object of the invention to provide a patient monitoring system having a minimum likelihood of electrical injury to a patient. More specifically, it is an object to provide a system whereby harmful electrical potentials are prevented from being transmitted to a patient through body-contacting sensors.
A further object of the invention is to provide self-contained apparatus for receiving, processing, and transmitting sensor-derived body-condition-related information to an electrical monitor, which apparatus provides electrical isolation of a sensor from the monitor, from induced alternating current at power line frequencies, and from the power source for the apparatus itself.
According to a preferred embodiment of the invention, such a system includes an electromedical sensor of a type requiring electrical excitation. The needed excitation is supplied by coupling a portion of the output from a battery-powered oscillator to this sensor. A second portion of the oscillator output is used to power an amplifier which receives body-condition-related information from the sensor. A third portion of the oscillator output serves to synchronize a detector in an output circuit which processes the amplified information for display or recording by a monitor.